7.3 Cell Structure Cell Transport Movement of materials Occur at boundaries (membranes) Two major types: Passive Active

Passive Transport Movement without the use of cellular energy Diffusion-particles move from high concentration to low concentration (any material) Equilibrium - equal concentration on both sides of the membrane

Facilitated diffusion-large molecules need help to travel across the membrane Uses protein channels Osmosis - diffusion of water Isotonic-diffusion of water Hypertonic - more Hypotonic - less

Active Transport Movement against a concentration gradient Requires energy Carried out by protein pumps Two processes that transport larger molecules Endocytosis — entering the cell Exocytosis — exiting the cell

Structure of the Cell Membrane Double layer (called lipid bilayer) Provides flexibility Lipids in membrane have two parts Hydrophilic (water loving heads) Hydrophobic (water fearing tails)